/******************************************************************************
* FILE: condvar1.c
* DESCRIPTION:
*   Example code for using Pthreads condition variables.  The main thread
*   creates three threads.  Two of those threads increment a "count" variable,
*   while the third thread watches the value of "count".  When "count" 
*   reaches a predefined limit, the waiting thread is signaled by one of the
*   incrementing threads.
*
* SOURCE: Adapted from example code in "Pthreads Programming", B. Nichols
*   et al. O'Reilly and Associates. 
* LAST REVISED: 9/20/98  Blaise Barney
******************************************************************************/

#include <pthread.h>
#include <stdio.h>

#define NUM_THREADS  3
#define TCOUNT 10
#define COUNT_LIMIT 12

int     count = 0;
int     thread_ids[3] = {0,1,2};


pthread_mutex_t count_mutex;
pthread_cond_t count_threshold_cv;

void *inc_count(void *idp) 
{
  int j,i;
  volatile double result=0.0;
  int *my_id = idp;

  for (i=0; i < TCOUNT; i++) 
  {
    count++;

    /* 
    Check the value of count and signal waiting thread when condition is
    reached.  Note that this occurs while mutex is locked. 
    */
    if (count == COUNT_LIMIT) {
      printf("inc_count(): thread %d, count = %d  Threshold reached.\n", 
             *my_id, count);
      }
    printf("inc_count(): thread %d, count = %d, unlocking mutex\n", 
	   *my_id, count);

    /* Do some work so threads can alternate on mutex lock */
    for (j=0; j < 1000000; j++)
      result = result + (double)random();
  }
  pthread_exit(NULL);
}

void *watch_count(void *idp) 
{
  int *my_id = idp;

  printf("Starting watch_count(): thread %d\n", *my_id);

  while (count < COUNT_LIMIT) {
    printf("watch_count(): thread %d Condition signal received.\n", *my_id);
    }
  pthread_exit(NULL);
}

int main()
{
  int i, rc;
  pthread_t threads[3];
  pthread_attr_t attr;


  pthread_create(&threads[0], NULL , inc_count, (void *)&thread_ids[0]);
  pthread_create(&threads[1], NULL , inc_count, (void *)&thread_ids[1]);
  pthread_create(&threads[2], NULL , watch_count, (void *)&thread_ids[2]);

  /* Wait for all threads to complete */
  for (i = 0; i < NUM_THREADS; i++) {
    pthread_join(threads[i], NULL);
  }
  printf ("Main(): Waited on %d  threads. Done.\n", NUM_THREADS);

  /* Clean up and exit */
  pthread_exit (NULL);

  return 0;
}
